Means for regulating centrifugal compressors.



RTEUGER.

MEANS FOR REGULATING GENTRIFUGAL GOMPRESSORS.

, APPLIUATION IILI EID FEB. 16, 19 12. 1,041,529.

Patented Oct. 15, 1912.

Inventor,

Witnesses;

lQichar-cl To all u'howz'. it may concern:

Be it known that I, RICHARD Trotter, a

RICHARD TRGGER, F CHARLOTTENBUBG, GERMANY, ASSIGEOB/ 'iO GENERALELECTRIC COMPAHY, A CORPGBATION OF NEW YGBK.

MEANS FOR nneULATrNG onnrnrruo'an ooiltrnnssoits.

Specification oi Letters Patent.

Application'filed February 16, 1912. Serial No. 673,923.

subject of the King of-Prussia, residing at Charlottenburg, Germany,have invented certain new and" useful Improvements in Means forRegulating Centrifugal Compressors, of which the following is aspecification.

In the operationof centrifugal air compressors when the load isdecreased to a small percentage of the total, a peculiar ac tion knownas surging or pumping takes place, meaning thereby that the air surgesto and fro in the compressor and in the pipingconnected thereto. For thepurpose of this case it is suflioient to say that surging is highlyobjectionable as it causes excessive .vibration and noise,.inte rfereswith the operation of the apparatus supplied with 'air,'

and decreases the economy of operation. It has been proposed to preventsurging by placing a blow-oft valve in-the discharge conduit that is'set to open automatically when thevolun'ie of air discharged by the,

compressor reaches a certain. relatively small value, said valveoperating in res spouse to a pressure difference-existing be tween twopoints in the discharge conduit. Since the valve always opens when theload decreases to said predetermined-low or criti-v cal value,it'follows that as the load is further decreased the energy required todrive the compressor will remain the same, be cause the amount of airpassingthrough the compressor will remain the same, butthe amount of airdischarged or escaping through the valve will, however, increaseas theload decreases. In other words, these compressors are inefiicient andwasteful-at light loads.

the present invention has for its object to provide .an improvedgoi'erning or regulating mechanism for compressors, whereby theireffective and efilcient range of opera tion can be increased, especiallyat. light loads. and the losses decreased. 7

In carrying-out my invention a blow-oh valve is placed in the dischargeconduit of .the compressor but instead ofbeing responsive to. a pressureditlerenceexistin'g on the discharge side of the compressor asheretofore, itis responsive to apressure diiterence existing onthe-inlet side. This pressure difference is obtained through. the use ofa suitable device such as Venturi tube, one side that said pressuredifference due to the action of the tube must bear a definite relationto-the volume air passing into-the compressor; By means of the throttlevalve, I can vary the output of the compressor over wide limits, and atthe same time the criti-' cal point-of opening of the blow-ofl' vulvewill be lowered as the lead. is decreased thereby decreasing the lossesheretofore mentioned. "To state the matter another. way, my inventioncomprises the feature that the pressure difference acting upon theblow-oil valve obtained from the part of the suction conduit of thecoi'npressor which follows a throttling member, so that the pressuredifference which is critical for the opening of the blow-oil'walvc ismade to depend upon the suction-pressure as regulated by'the throttlingmember.

In the accompanying drawing, which illustrates one of the/embodiments ofmy invention, is shown a multistage centrifugal air compressor and theregulating mechanism therefor.

1 indicates a multistage centrifugal air compressor of any suitabletype. It driven by a motor 2 shown in dotted lines,

which may be an electric motor a st am The compressor;

pipe 8 that leads to the motor'for actuating the blow-off valve as willappear later. 9 indicates a pipe connected to the inlet conduit at orabout the discharge end of the tube. This also conveys fluidunderpressure'to the motor for actuating the blowpfi valvef Between thethroat-6 and the end of the tube a pres'sure ditlerence exists when airor other fluid is tlowingthrough the inlet conduit.- This pressurelgliiiierence will depend upon the amount of fluid flowing, it'

Patentedflct, 15,1912.

being greater as the amount of fluid in creases. The pressure existingat the throat 6 will be less than that existing at the dis-' thethrottling effect of thevalve 10 can be adjusted. a

4 The construction and arrangement of the blow-ofl valve will now bedescribed: Connected to the discharge conduit tor formed integraltherewith is a c linder 14 containing a piston valve 15, t e latterbeing arranged to move up and down to cover and uncover the dischargeports 16 shown -.in

dotted lines. The valve is actuated by a piston ;17 located in theenlarged cylinder 18. Between the upper side of the piston.-

and the head of the cylinder is located a compression spring 19 thatnormally tends to push the valve 15 downward and open the orts 16 andpermit air to escape. This tenciency is opposed by the pressure differ.ence created by the device. located in the inlet conduit, 2'. e., theVenturi tube.

In 'rrderto-balance the pressures on opposite sides of the valve 15, abypass 20 is provided that connects the conduit 4 with the cylinderl t.

The fluid pressure above the piston 17 is less. than the fluid pressure'below it. So long as the compressor is working above a certain minimumload, the fluid pressure under the piston 17 will be suflicient toovercome the effect of the fluid pressure received from the pipe 8 andthe force exerted by the spring 19, but when the load is decreased tosuch a'low value that surging could take place, the pressure difieren'cedue to the Venturi tube decreases, so'that the pressure of the spring 19when added to that of the fluid received from the pipe 8 .will besufli-.;

cient to open the valve '15, and discharge air through the ports 16. Itwill thus be seen that the valve 15 forms a means for insuring a certainminimum load for the com pressor and its driving motor, which load issuperior to that at which surging can take place. Furthermore, since thethrottle valve precedes the device for creating pressure difference itfollows that the latter is under the control of said valve. Such beingthe case, the blow-off valve'instead of opening at all times un'der-thesame load conditions, will open at' different load conditions dependingu on the throttling efifect n other words, the range of the .valve 10;

of operation of the-compressor can be increased by my improvedarrangement, owing to the fact that the blow-off valve is not set foronefixedminimlun load, but is-set to operate at an infinite number ofload values, dependingupon the position of the throttle valve. Assumingthe compressor to be in service and that the consumption of compressedair decreases for any cause, the throttle valve being wide. open. Withthe decrease in consumption, the pressure difference act-ing on thevalve 15 correspondingly decreases and at' a certain minimum workperformance of the compressor, the blow-off valve will open anddischarge air. The operator on observing this fact, can, by throttlingthe inlet conduit, reduce the work performance ofthe compressor withincertain limits I without, however, causing surging, and at 85, the sametime the further opening of the blow-off valve will be retardeddepending upon'the degree of throttling.

In accordance with the provisions of the "patent st atutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof;but

I desireto have it understood that the apparatus shown is onlyillustrative, and that the inventioncan be carried out by other means.What I claim as new and desire to secure I by Letters Iatent of theUnited States, is .1. In combination, a' centrifugal com J."

ressor having an inlet and a discharge consuit, a blow-ofl' valve fordischarging fluidunder pressure from I the compressor, a throttle valvein the inlet, and a means lo- 'cated on "the compressor side ofthe'throttle and sensitive to a change in the rate of flow of fl'uipassing through it for actuating the blow-oft valve.

2. Incombination, a centrifugal comressor having an inlet and adischarge conuit, a 'bloW-ofi' valve in the discharge mm duit, a meanssensitive to, a change, in the rate of flow of fluid passing through thein- .let for controlling the operation of the .blowoil'- valve, and amemberfor throttling the passageof fluid prior to its entrance to the 5inlet and said means' j 3. In combination, a centrifugal comressorhaving an inletand a discharge consuit,- a blow-ofl' valve in thedischarge conduit, a-means located in the inlet for creat- 2 ing aressure difference responsive to changes In the rate of flow of thefluid passing through the compressor, a means for actuating the blow-offvalve that is responsive to sai pressure difierence, and a throttlevalve that is located in the inlet and precedes the said means. 4.1acombination, a centrifugal compressor] having. an inlet and a dischargeconduit, ablow-ofi .valve in the discharge '1,04 1,529 p p i 3 conduit,means tending at allftimes to open and athrottle valve that is locatedon-the inlet side of said device.

In combination, a cont-rifugal compressor having an inlet and adischarge coniluit, a blow-off valve in the discharge con :Iuit. that isarranged to open when the load 0;; the compressor falls below a certainvalue. a means actuated by fluid under-pressure for holding the valveclosed, a Venturi tuhefor creatmg a pressure dlfference, condu tsconveying fluld under pressure from the tube to the'saidmeans, and athrottle valve in the inlet conduit for controlling the amount of fluidthat passes through said 20 tube.

6. In combination, a centrifugal compressor having anmlet and adlscharge con- .duit, a blow-oft" valve inthe discharge conduit thatopens under conditions ofdecreas, 25 mg load, a Venturi tube in theinlet conduit for controlling the action of the valve, and a throttlevalve that regulates the admission of fluid to said tube Inwitnesswhereof, I have hereunto set 30 my hand this dayof26th January, 1912.RICHARD TRoeER. Vitnesses:

JULIUS RIENLAND, OSKAR SINGER-A Copies of this patent may be obtainedfor five cents each, by addressing the. Commissioner of Patents,

' a Washington, D. C. i

